Development of infrastructures for data communication networks has enabled applications to use high processing performances of networks. Such networks are highly scalable and, hence, various and many information services will definitely be made available through the networks in the future.
On the other hand, thus far, only a few experts could adjust configurations of such networks and it has been very difficult for a general user to adjust a network in accordance with his/her applications. This is the same if a network is limited to one company, one university or the like. When an unexpected event occurs, even a network administrator finds it difficult to cope with it.
It is sometimes desirable to collect and process various data provided on a network, in a limited time, for a prescribed object. By way of example, when a sudden disaster hits or is expected, if a large amount of information related to situations of damage, information related to events as possible cause of the disaster and so on could be collected and processed timely, it would be possible to prevent further damage or to take necessary measures to the damage. For this purpose, it is necessary to collect formidable amount of data dispersed on the network, combine various and many information services and to execute them in an efficient manner.
In order to realize such an application, a technique that sends a request for an information service accurately and timely to a network and dynamically adjusts configuration of the network is necessary. Particularly when information generated suddenly in a scale beyond expectation is to be transferred timely by flexibly selecting paths, when a huge amount of information is to be analyzed through trial and error, or when information service is to be provided in accordance with urgency of application or importance of data, it is desirable to flexibly configure a network in a manner coordinated with the request of information service, to prevent excessive increase of cost for network management and for development of information services.
Consider a common network. On the one hand, when an application developer wishes to create a new service cooperation on-demand, only the network paths that have already been set can be used, and hence, it is impossible to maximize network performance appropriate for the information service. On the other hand, a network administrator builds a network under conditions assumed in advance and, therefore, if a trouble such as unexpected traffic overloads on an assumed path occurs, it is difficult to address the problem on highly real-time basis.
A basic technique solving these problems and enabling flexible configuration of networks is so-called Software-Defined-Network (SDN), described in M. Nick, A. Tom, B. Hari, P. Guru, P. Larry, R. Jennifer, S. Scott and T. Jonathan, “OpenFlow: Enabling Innovation in Campus Networks,” SIGCOMM Computer Communication Review, pp. 69-74, 2008. SDN is a technique for setting topology and QoS (Quality of Service) of a network by software and for forming a physical network by calling an API (Application Programming Interface) or a command. SDN enables programming of a network configuration in a similar manner as software programming, and enables virtually forming a network (virtual network) on a physical network.
OpenFlow is one of the representative techniques of such SDN. OpenFlow divides functions of conventional network devices to one referred to as OpenFlow controller and ones referred to as OpenFlow switches. Devices on a network are connected to OpenFlow switches, and data can be transferred between each of OpenFlow switches.
Referring to FIG. 1, a network realized by OpenFlow (OpenFlow network) 30 includes a group 40 of switches including OpenFlow switches 50, 52, 54, 56 etc. actually in charge of communication and an OpenFlow controller 42 monitoring and controlling states of switch group 40. Switching by each of the switches in group 40 can dynamically be controlled through OpenFlow controller 42 in accordance with a procedure referred to as OpenFlow protocol.
OpenFlow network 30 can be controlled by software. When a user gives an instruction of a network control command for realizing a logical configuration of a virtual network to OpenFlow controller 42, OpenFlow controller 42 forms a flow table for realizing the logical configuration on a physical network, and distributes it to each of the OpenFlow switches 50, 52, 54 and 56. Each of the OpenFlow switches 50, 52, 54 and 56 transfers data in accordance with the flow table. On the other hand, the OpenFlow switches 50, 52, 54 and 56 each transmit bandwidth information of the network and the like to OpenFlow controller 42. Based on these pieces of information, OpenFlow controller 42 dynamically modifies the flow table to realize the instructed configuration of virtual network.
In this manner, the user can build a virtual network, independent from the configuration of physical network. It is unnecessary to have full knowledge of the physical network for this purpose.
On the other hand, an actual network administrator need to know on real-time basis pieces of information related to what type of virtual network is formed on the physical network of which he/she is in charge, how much traffic each path of the physical network has and so on. Since a huge number of devices are connected to the network, it is impossible by text information to comprehend such type of information.
Japanese Patent Laying-Open No. 2012-209871 (hereinafter referred to as '871 Reference) discloses a solution to such a problem. Referring to FIG. 2, a network management screen 60 of a network visualizing apparatus disclosed in '871 Reference allows management of physical network resources allocated to a plurality of virtual networks. Network management screen 60 includes: a VNT selection window 70 allowing selection of a virtual network to be displayed; a physical net window 80 displaying nodes included in a physical network and links (physical links) between each of the nodes; VNT windows 72 and 74 displaying logical links and routers forming the VNT selected by VNT selection window 70; and distributed resources windows 76 and 78 displaying, for each VNT, resources (physical topology of VNT and bandwidth allocated to links) allocated to each VNT. On VNT windows 72 and 74, traffic amount of data flowing through each link is also displayed.
When a link on the physical network is shared by virtual networks of which number is equal to or larger than a prescribed threshold value, physical net window 80 displays an alarm in the vicinity of the link. By way of example, in FIG. 2, there is an indication “S1 1G, S2 1G” near a link 82. This means that this link 82 is shared by virtual networks S1 and S2 and bandwidth allocated to these are 1G each. A similar indication shows that link 84 is shared by four virtual networks S1, S2, S3 and S4, and the bandwidths allocated thereto are 1G, 1G, 1G and 8G, respectively.
According to this reference, network management screen 60 as such allows the network administrator to view the state of sharing, status of resources allocation and behavior of each virtual network on the physical net, making it easier to grasp the status of virtual networks.